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KVM: x86: Fix kvmclock bug 

If preempted after kvmclock values are updated, but before hardware
virtualization is entered, the last tsc time as read by the guest is
never set.  It underflows the next time kvmclock is updated if there
has not yet been a successful entry / exit into hardware virt.

Fix this by simply setting last_tsc to the newly read tsc value so
that any computed nsec advance of kvmclock is nulled.

Signed-off-by: Zachary Amsden <zamsden@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Zachary Amsden 2010-09-18 14:38:12 -10:00 committed by Avi Kivity
parent 0959ffacf3
commit 28e4639adf
1 changed files with 1 additions and 0 deletions
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arch/x86/kvm/x86.c
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@ -1095,6 +1095,7 @@ static int kvm_write_guest_time(struct kvm_vcpu *v)
vcpu->hv_clock.tsc_timestamp = tsc_timestamp;
vcpu->hv_clock.system_time = kernel_ns + v->kvm->arch.kvmclock_offset;
vcpu->last_kernel_ns = kernel_ns;
vcpu->last_guest_tsc = tsc_timestamp;
vcpu->hv_clock.flags = 0;
/*